Sound Waves

Sound is a mechanical vibration transmitted through an elastic medium traveling in air at the speed of approximately 1088 feet per second at sea level. The behavior of sound propagation is affected by three things, first relationship between density and pressure, second by motion of the medium, and third the velocity of the medium. And wave is a disturbance that propagates from one place to another; waves propagate with well defined speeds determined by the properties of the material through which they travel. In addition, waves carry energy for example; part of the energy you put into sound waves when you speak is carried to the ears of others where some of the sound energy is converted into electrical energy by nerves impulses to the brain which, in return creates the sensation of hearing.

It is important to distinguish between the motions of the wave itself and the motion of the individual particles that make up the wave. Common examples include the waves that propagate through a field of wheat. The individual wheat stalks sway back and forth as a wave passes, but they do not charge change their location. Similarly a wave at a ball game may propagate around the stadium more quickly than a person can run, but the individual people making up the wave simply stand and sit in one place. From these examples it is clear that waves can come in a variety of types. Perhaps the easiest type of waves to visualize is a wave on a string, to generate such a wave, start by tying one end of a long string or rope to a wall. Pull on the free end with your hand producing a tension in the string, and then move your hand up and down, as you do so, a wave will travel along the string toward the wall, in fact your hand moves up and down with a simple harmonic motion, the wave on the string will have the shape of a sine or a cosine we refer to such a wave as a harmonic wave.